This research integrates the expertise of two New Investigators to examine cognitive impairments in autism. Persons with autism show substantial cognitive impairments in a wide array of thinking skills. However, most of the documented cognitive impairments in autism are for skills that normally develop after the symptoms of autism appear. Symptoms of autism appear within the first year of life suggesting that cognitive impairments must also be present during the first year. It is proposed that persons with autism are impaired in implicit learning, an early-developing precursor to many of the impaired late-developing cognitive skills that have been documented in autism. Implicit learning is an automatic cognitive process that takes place independently of conscious attempts to learn and in the absence of explicit knowledge of what was learned. Implicit learning plays an important role in both language learning and social understanding, two areas substantially impaired in autism. It is hypothesized that children with autism use explicit, effortful processes to compensate for implicit learning deficits. This explicit approach to understanding social and language information could lead to the repetitive behaviors present in autism. This theory is examined in a series of experiments that utilize rigorous cognitive neuroscience/information-processing methodologies. These experiments establish whether implicit learning impairments are present in persons with autism using a larger sample of individuals who possess a wider range of intellectual abilities than was used in pilot research. Two implicit learning tasks are used to establish the generality of findings. The hypothesis that persons with autism use explicit processes to complete implicit learning tasks is tested by examining the role of individual differences in explicit processing. Finally, this research uses correlational methods to examine whether performance on implicit learning task is related to behavioral symptoms of autism including poor social and language skills and repetitive/ritualistic behaviors. Documentation of this type of cognitive impairment could help to explain some of the behavioral symptoms of autism, could have implications for diagnosis and intervention strategies, and could guide the search for underlying brain dysfunction in autism.